At present, there are “WiMAX” (see for example Non-patent Reference 1 below) and “3GPP” (see for example Non-patent Reference 2 below) as communication standards for portable telephones and other mobile terminals.
FIG. 20 depicts an example of the configuration of a communication system 100 of WiMAX (see for example Non-patent Reference 3 below). The communication system 100 includes a MS-A (Mobile Station-A) 10, BS group 20, ASN-GW group 40, and CSN group 60.
The BS group 20 includes a plurality of BS (Base Station, BS#1 to #4) 21 to 24; the CSN-GW group 40 also includes a plurality of ASN-GW (Access Service Network-GateWay, ASN-GW#1 to #4) 41 to 44.
The ASN-GW 41 to 44 are gateways to provide the MS-A 10 with access to the network (including the ASN group 40 and CSN group 60). The CSN group 60 includes a device to provide service to the MS-A 10, which may for example be equivalent to a service provider or similar. FIG. 19 depicts an example includes four BS 21 to 24 and four ASN-GW 41 to 44.
Each of the BS 21 to 24 includes two entities (function blocks) which are PA (Paging Agent) 211, 221, 231, 241, and DP (Data Path) 212, 222, 232, 242.
The PA 211, 221, 231, 241 handle conversation between the PC (Paging Controller) 411, 421, 431, 441 of the ASN-GW 41 to 44 and IEEE 802.16e.
The DP 212, 222, 232, 242 (also called transmission portion) perform selection of input data packets and similar, and transmission of data to the MS-A 10 and similar.
On the other hand, each of the ASN-GW 41 to 44 also includes PC/LR (Location Register) 411, 421, 431, 441, DP/FA (Foreign Agent) 412, 422, 432, 442, and Auth (Authenticator) 413, 423, 433, 443.
The PC/LR 411, 421, 431, 441 strictly speaking include two entities, the PC and LR, but are executed as a single block when executing various operations, and so are depicted as single entity in the drawing. Similar remarks apply to the DP/FA 412, 422, 432, 442 (also called communication portion).
The PC is an entity which manages operation of the MS-A 10 in idle mode (the state in which the power supply to the MS-A 10 is turned off), and the LR is a distributed database having information related to the MS in idle mode. The FA is a router, positioned in a Foreign Network of the MS-A 10, which notifies the HA 61, 62 of the position of the MS-A 10 and relays and transfers data of the MS-A 10.
The Auth 413, 423, 433, 443 provide links with the MS-A 10 and an AAA server 63 at the time of authentication, and operate as client of the AAA server 63. The Auth 413, 423, 433, 443 hold information relating to authentication and perform key management (holding authentication key issued by the AAA server 63 and similar), and for example transmit authentication keys to MS-A 10 via the BS 21 to 24.
The CSN group 60 includes HA (Home Agent) 61 and 62 and the AAA (Authentication, Authorization, and Accounting) server 63.
The HA 61, 62 are routers, positioned in a Home Network of the MS-A 10, which ascertain the network in which the MS-A 10 is positioned and deliver data to the MS-A 10.
The AAA server 63 is a server which performs authentication of the MS-A 10 and similar, and for example holds authentication keys for each MS and outputs the authentication key to the MS-A 10 for which there has been a connection request.
As depicted in FIG. 20, the HA 61 is connected to the ASN-GW 41 and 42, and the ASN-GW 41 and 42 are respectively connected to the BS 21 and 22. Further, the HA 62 is connected to the ASN-GW 43 and 44, and the ASN-GW 43 and 44 are respectively connected to the BS 23 and 24.
The communication system 100 configured in this way operates as follows (see for example Non-patent Reference 3 below). First, when the MS-A 10 initially connects to the network (Initial Network Entry), the DP 222 of the BS 22, DP/FA 422 of the ASN-GW 42, HA 61 of the CSN group 60, and AAA server 63 operate, based on a connection request of the MS-A 10, and identification information for each MS-A 10 such as an IP address of the MS-A 10 is held. Then, data from the network is transmitted from the HA 61, via the DP/FA 422 and DP 222, to the MS-A 10.
Thereafter, the MS-A 10, as the active state, transmits and receives data via the BS 22 with the network.
Then, when the MS-A 10 moves into the cell range of the BS 23 and the power supply of the MS-A 10 is cut off, the MS-A 10 transmits and receives message with the PC/LR 431 of the ASN-GW 43 via the BS 23. Hence when in the idle state, the PC/LR 431 is active, and the PC/LR 431 holds identification information for the MS-A 10.    Non-patent Reference 1: IEEE 802.16e-2005    Non-patent Reference 2: 3GPP TS 23.060 V4.7.0 (2002-12)    Non-Patent Reference 3: WiMAX Forum Network Architecture Release 1.0.0, Mar. 28, 2007
Focusing on the ASN-GW group 40 in the above-described example, the operating entities are different according to the state of the MS-A 10. That is, when the MS-A 10 is in the active state, for example the DP/FA 422 of the ASN-GW 42 and Auth 423 operate, and when in the idle state, for example the PC/LR 431 of the ASN-GW 43 operates. And, connections of these entities 422 and similar with the MS-A 10 are currently established, the ID of the MS-A 10 is held, and service is provided.
In a certain time period, the entity 411 or similar of one among the ASN-GW 41 to 44 operates, and which entity 411 or similar operates changes according to the state of the MS-A 10 and similar.
In this state, when an attempt is made to search for the current position of the MS-A 10, for the operating entity 411 and similar is searched, all of the entities 411 and similar of all of the ASN-GW 41 to 44 in the ASN-GW group 40 must be searched. As a result, a resource of the communication system 100 is spent merely on searching. Moreover, when all of the entities 411 and similar are searched, an extremely long time is spent on searching, and such a method is not effective for providing service which includes search.
On the other hand, an entity called an HLR (Home Location Register) performs centralized management of the MS-A 10 in a 3GPP communication system, as also disclosed in the above-described Non-patent Reference 2. Hence in 3GPP, in order to search the current position of the MS-A 10, it is sufficient to access the HLR and perform a search.
In WiMAX, there is no entity which performs centralized management of the current positions of the MS-A 10 as in 3GPP, and so in order to search for the current position of the MS-A 10, a communication system in which resources are utilized effectively, and search times can be shortened, is desirable.